1. Technical Field of the Invention
This invention relates to telecommunication systems and, more particularly, to an integrated radio telecommunications network which interworks circuit switched services and packet switched services, and to a method of interworking an ANSI-41 radio telecommunications network and the General Packet Radio Service (GPRS) packet data network.
2. Description of Related Art
Two approaches to data switching are circuit switching and packet switching. Plain old telephone service (POTS) and cellular voice services, for example, use circuit switching. Fixed circuit switching paths are set up between the parties involved in a call by exchanging signaling messages which contain the parties"" addresses and request the establishment of a physical switching path. The signaling messages are exchanged between the addressees and switching centers, and between switching centers. The switch(es) respond to the requests in the signaling messages by establishing the physical switching path between the addressees. A data switch can be set up in a similar manner to provide circuit switched data services.
Packet switching, on the other hand, utilizes data packets which are comparatively short blocks of message data. The packets may be of fixed length as in asynchronous transfer mode (ATM), or may be of variable length as in frame relay or the Internet protocol (IP). Complete data messages are broken down into short packages, each with a header. These packets may be sent on diverse routes to their eventual destination. Because packets often travel on diverse routes, they may not arrive at the far-end receiving node in sequential order. Thus, the far end node must have the capability to store incoming packets and rearrange them in sequential order. The destination node reformats the message as it was sent by the originator and forwards it to the final destination user. Packet switching can be considerably more efficient when compared to circuit switching due to the multiplexing effects which make better use of the available transport bandwidth. Each service or user utilizes only the bandwidth it needs, leaving the unused bandwidth for other services/users. A plurality of paths must exist from the originating node to the destination node for in-service performance since an alternate route may be utilized in the event of failure or congestion of a given route.
GPRS is a packet data transmission service which is designed to function with the Global System for Mobile Communications (GSM) to enable mobile stations (MSs) to access both voice/circuit switched and packet data network services. A proposed GPRS packet data standard defines MS service classes and infrastructures to enable MSs to utilize the GPRS network. However, the GPRS standard addresses interworking requirements for GSM, but does not address interworking requirements for radio telecommunications networks based on ANSI/TIA standards such as those utilized throughout most of North America. The network architecture and the interface between the packet-data-specific nodes and the circuit-switched-specific nodes is tailored to GSM. GPRS does not fit within the ANSI-41 network. A system and method of interworking GPRS and ANSI-41 networks is needed so that the full GPRS functionality (e.g., services, interface protocols, node functionality, etc.) can be supported from the perspective of radio access logic, network logic, and service logic in ANSI-41 networks.
Today, ANSI-41 and ANSI-136 networks only provide voice or circuit-switched services. Therefore, an operator cannot benefit from the advantages and flexibility that packet switching provides when the operator is providing Internet access to subscribers utilizing ANSI-41/136-based cellular networks. A dial-up direct access connection or an analog modem connection must be made to the Internet. For a dial-up direct access connection, for example, a circuit-switched connection is provided between a MS and an Internet access gateway. A call is set up to the gateway, and then a Transmission Control Protocol/Internet Protocol (TCP/IP) session to an Internet provider is set up on top of that connection. This solution does not provide the benefits of multiplexing over the air interface and through circuit switching facilities since dedicated resources are utilized for the duration of the Internet connection. This is very inefficient since, in a typical Internet connection, packets of data are not continuously being sent over the connection. Thus, a voice channel over the air interface is tied up for the duration of the Internet connection, and associated circuit-switched resources over the network are not optimally utilized.
The existing solution is also not very flexible in terms of packet data network access because only one connection can be made at a time. It is not possible to make multi-party call connections for data calls in the way that multi-party voice connections can be made. Thus, simultaneous circuit switched voice and data services cannot be provided while connected through a circuit-switched connection to the Internet. If a voice call is routed to a mobile station during an Internet session, the subscriber cannot take the call and then rxc3xa9sumxc3xa9 the Internet connection in a seamless fashion. The voice call must be rejected, routed to voice mail, or routed to another number. Additionally, the user cannot originate voice calls during a data call because the data call is circuit-switched between the mobile station and the Internet access gateway.
In order to overcome the disadvantage of existing solutions, it would be advantageous to have a method of integrating GPRS packet switched services and infrastructure with the ANSI-41 circuit switched services and infrastructure, thus enabling similar services to those available in GSM. The present invention provides such a method and integrated network.
In one aspect, the present invention is an integrated radio telecommunications network which integrates an ANSI-41 circuit switched network and a General Packet Radio Service (GPRS) packet data network. The integrated radio telecommunications network includes a mobile switching center (MSC) in the ANSI-41 network that provides circuit switched services to a mobile station which operates in both the ANSI-41 network and the GPRS network, and a serving GPRS switching node (SGSN) in the GPRS network that provides packet switched services to the mobile station. An interworking function interfaces the MSC with the SGSN, and maps circuit switched signaling utilized by the MSC into GPRS packet switched signaling utilized by the SGSN, and maps GPRS packet switched signaling into circuit switched signaling. An interworking GPRS base station controller interfaces the SGSN with a GPRS/ANSI-136 base station which supports both ANSI-136 operations and GPRS operations. The interworking GPRS base station controller adapts a signaling format utilized by the SGSN into an air interface signaling format and passes traffic signaling between the SGSN and the GPRS/ANSI-136 base station. The network also includes means for transparently transferring ANSI-136 information between the mobile station and the ANSI-41 network by adding the ANSI-136 information to selected GPRS messages.
The ANSI-136 information which is added to the selected GPRS messages may include registration and authentication information such as a Mobile Identification Number (MIN), an Electronic Serial Number (ESN), and an ANSI-41 Authentication Response (AUTHR). The selected GPRS messages to which the ANSI-136 information is added include an Attach Request message which is sent from the mobile station to the SGSN during a GPRS Attach procedure, and a Location Updating Request which is sent from the SGSN to the interworking function that interfaces the MSC with the SGSN.
In another aspect, the present invention is an integrated radio telecommunications network which integrates an ANSI-41 circuit switched network and a GPRS packet data network which includes a Class D mobile station which operates only over 30-kHz channels in both the ANSI-41 network and the GPRS network. An MSC in the ANSI-41 network provides circuit switched services to the mobile station, and a serving GPRS switching node (SGSN) in the GPRS network provides packet switched services to the mobile station. An interworking function interfaces the MSC with the SGSN, and maps circuit switched signaling utilized by the MSC into GPRS packet switched signaling utilized by the SGSN, and maps GPRS packet switched signaling into circuit switched signaling. An interworking GPRS base station controller interfaces the SGSN with a GPRS/ANSI-136 base station which supports both ANSI-136 operations and GPRS operations. The interworking GPRS base station controller adapts a signaling format utilized by the SGSN into an air interface signaling format, and passes traffic signaling between the SGSN and the GPRS/ANSI-136 base station.
The Class D mobile station is equipped with an International Mobile Station Identification (IMSI) which is utilized in the GPRS network. The interworking function includes means for translating the Class D mobile station""s Mobile Identification Number (MIN) utilized in the ANSI-41 network into an associated IMSI utilized in the GPRS network. The integrated radio telecommunications network may also include a GPRS Home Location Register (GPRS HLR) in the GPRS network which authenticates the Class D mobile station for packet data purposes, and an ANSI-41 home location register/authentication center (HLR/AC) in the ANSI-41 network which authenticates the Class D mobile station for circuit switched purposes. The integrated network may also include a Class E mobile station which operates only over 30-kHz channels in the GPRS network. The Class E mobile station camps on a packet control channel (PCCH) as its normal mode of operation and only changes to a digital control channel (DCCH) at power-up to verify packet data service availability. The Class E mobile station is equipped with an IMSI, and the GPRS HLR includes means for authenticating the Class E mobile station.